xt7vhh6c4635 https://exploreuk.uky.edu/dips/xt7vhh6c4635/data/mets.xml   Kentucky Agricultural Experiment Station. 1977 journals 227 English Lexington : Agricultural Experiment Station, University of Kentucky Contact the Special Collections Research Center for information regarding rights and use of this collection. Kentucky Agricultural Experiment Station Progress report (Kentucky Agricultural Experiment Station) n.227 text Progress report (Kentucky Agricultural Experiment Station) n.227 1977 2014 true xt7vhh6c4635 section xt7vhh6c4635                          
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I Kind of Forage, Forage Management and Creep Feed for Spring-Calving
Cows and Calves .............................. 5
Rumensin for Growing, Finishing Cattle ....................... 11
Monensin Levels for Steer Calves Grazing Pasture ................... 11
Monensin Levels for Finishing Steers Fed Corn Silage Diets ............... 12
Effects of Different Rumensin Levels on Feedlot Cattle ................. 14
High and Low Levels of Corn and Wheat With and Without Rumensin
in F eedlot Rations ............................. 15
Acidosis of Feedlot Cattle ............................ 20
A Improving Kentucky Forages by Use of Better Management ............... 23
‘ Backgrounding Guidelines ............................ 25
Sheep and Cattle: Companion Grazing for Increased Profit ............... 30
Essentials of Good Corrals ............................ 33
Results of Extension Demonstrations in Animal Science ................ 36 V
Sale of Feeder Cattle in Selected Kentucky Auction Markets ............... 39
Feeder Calf Sales Report - Fall 1976 - Spring 1977 .................. 44
Preventive Medicine Calendar for Spring Calving Beef Cows ............... 48
Summary of Performance Tested Bull Sales in 1977 .................. 50
Growth of Steers Fed Soybean Meal or Urea Supplemented With Different
I Levels of Sulfur .............................. 52
Wintering Steer Calves .............................. 54
Response of Steers Fed Different Protein Levels and Corn Silage ............. 56
Noncontinuous Protein Levels for Growing Calves ................... 57
Fat Treatment of Protein for Steers ........................ 59 .
Rumen By-Pass in Cattle ............................ 60
Amino Acid Metabolism by Rumen Microbes ..................... 62
Nucleic Acid Metabolism and Digestion in the Digestive Trace of Ruminants ......... 64
Liver Arginase Activity in Steers Fed Diets Containing Different Levels of Protein ....... 66
Magnesium Metabolism in Fall-Calving Beef Cows ................... 68
Blood Metabolites in Spring-Calving Cows Exhibiting Grass Tetany ............ 70
Mineral Utilization in Sheep at High Temperatures ................... 72
Mineral Balance in Sheep Fed Early Spring Dehydrated Forages .............. 73
Stability of Vitamin A and Chlortetracycline Added to Liquid Supplements
for Beef Cattle ............................... 74

 Evaluation of Four Varieties of Tall Fescue for Yearling Steers During the
Spring-Summer Grazing Season ........................ 75
Relationship of Breed and Sex on Beef Muscle Fiber Traits ............... 77
Relationship of Feeding Methods on Beef Muscle Fiber Characteristics ........... 80 ·
Relationship of Muscle Fiber Characteristics on Beef Palatability and Carcass Traits ...... 83 .
Effects of Thawing Methods and Subsequent Cookery on Beef Quality
and Eating Traits .............................. 86
Microwave VS Conventional Cookery of Beef Cuts ................... 90
Carcass Characteristics and Composition and Consumer Acceptance of
Baby and Limited Grain Finished Steers .................... 94 A
Effects of Post-Mortem Aging and Cooking Temperature and Rate on Selected
Tenderness Related Characteristics of Bovine Muscle ................ 98
List of Beef Cattle Publications Available for Distribution ................ 99

N. W. Bradley, D. R. Lovell,]. A. Boling and Nelson Gay
Kentucky 31 fescue and Kentucky bluegrass are both important cool-season grasses in Kentucky.
A four-year experiment summarized in 1975 (Kentucky Agricultural Experiment Station, Progress
Report 218) showed that fescue-clover pastures produced more total feed during the year, but blue-
grass-clover pastures were of higher quality.
Pastures were stocked at the rate of one cow and calf for each two acres and any surplus forage
was harvested as hay. During the four year period, the fescue-clover pastures yielded almost three
i times as much hay as the bluegrass-clover pastures. Cows on the fescue-clover pastures also required
about 21% less hay during the winter, indicating that fescue-clover pastures also provided more feed
during the winter than bluegrass-clover pastures. The higher quality of bluegrass-clover pastures was
_ reflected by 48 pound heavier weaning weight of calves.
_ Further evidence of quality of pasture was that creep feeding calves on bluegrass-clover pastures
~ resulted in a 38 pound heavier weanir1g weight; whereas creep feeding on fescue-clover pastures
‘ resulted in weaning weights which were 72 pounds heavier than non-creep fed calves. If the goal of a
cow-calf producer is maximum weaning weight, this can be achieved by using bluegrass-clover or by
creep feeding on fescue-clover. Creep-fed calves grazing fescue-clover pasture had weaning weights only
14 pounds lighter than creep-fed calves grazing bluegrass-clover.
In view of the greater amount of feed produced from fescue plus the fact that it is by far the
most used cool-season grass in Kentucky, further research on management options seems justified. The
experiment reported here included the following variables:
Kind of grass 1. fescue
2. bluegrass
Forage management 1. grass—nitrogen
2. grass-clover
Creep feed 1. none
2. cracked corn
The experimental design is shown in table 1. A total of 120 Angus cows and calves were used
each year for a three-year period. Two acres of pasture were used for each cow and calf and surplus
forage was harvested for hay. Eight groups of 15 cows and calves each were assigned to the eight .
different experimental treatments. Each group of 15 cows and calves was assigned to a 30-acre pasture.
The pasture was subdivided into four 7.5 acre pastures to permit rotational grazing. An attempt was
made to keep the pastures of high quality by clipping seed heads, weeds and forage which had been
refused immediately following removal of cattle from the pastures.
Grass pastures were fertilized with about 140 pounds of actual nitrogen applied in split applica-
tions in March and August. Grass-clover pastures were seeded each March with two pounds per acre of
Ladino clover. A chain harrow was then used to spread manure piles and as an aid in getting the clover
‘ seed in contact with the soil to assure better germination.
I Cows were bred May 20 to july 20 and calves were born during March and April. Calves were
weaned in October at about 220 days of age. Calves were removed from the experiment at weaning,

Table 1. Experimental Design
Kentucky 31 Fescue Kentucky Bluegass
Ladino Ladino ·
Nitrogen Clover Nitrogen Clover
No Creep 15* 15 15 15
Creep 15 15 15 15
* 15 cows and calves for each of the eight treatments
but cows remained on the experimental pastures throughout the year. When supplemental feed was
needed during the winter, cows were fed hay which had been harvested from the pastures to which
they were assigned. In the case of bluegrass-clover, total hay produced was not sufficient to meet the
demands of cows on this treatment and bluegrass-clover hay was obtained from other sources. In A
addition cows were given extra energy in the form of ground corn for approximately a two-month .
period beginning about the middle of February. Corn was fed at the rate of 3.5 pounds per cow daily. ·
A source of calcium, phosphorus and salt was also available at all times. During the winter feeding
period, a mixture of 6 parts salt, 3 parts magnesium oxide and 1 part vitamin A concentrate (30,000
IU/gram) was offered free choice. In a further attempt to prevent grass tetany, 2 ounces of magnesium
oxide per cow daily were included in the corn which was fed for about a two-month period beginning
two weeks before calving started.
Calves assigned to the creep feeding treatments were given cracked yellow shelled corn on a free
choice basis. Calves were offered the creep feed from May 20 until weaning.
Cows were reallotted each spring following the calving season and before breeding started on May
20. An attempt was made to equalize sire of the calf, sex of the calf and age of the cow.
Pasture samples were taken during the period of May and June and again during September from
each pasture each year. The average composition of pastures is given in table 2. In the category of
"other grass", most of the other grass in the fescue pastures was bluegrass with a lesser amount of
orchardgrass. Most of the other grass in the bluegrass pastures was orchardgrass with a lesser amount of
fescue. Obviously an attempt to eliminate the bluegrass from areas to be seeded in fescue by spraying 1
with herbicide before fescue was seeded was not completely successful.
Table 2. Pasture Composition (3-Year Average*)
Kentucky 31 Fescue Kentucky Bluegrass
Nitrogen Clover Nitrogen Clover
Bluegrass, % ····   87.0 42.6
Fescue, % 72.4 53.7 ——-- ---- _
Clover, % 0.5 18.1 4.2 20.6
Other Grass, %** 21.3 22.2 4.5 16.8 i
Weeds, % 5.0 5.9 4.5 20.0 '
*A total of 20 samples was taken for each of the pastures over a 3-year period.
**lncludes any fescue present in the bluegrass pastures and any bluegrass present in the
fescue pastures.

Table 3 gives the three-year average performance data of calves. Using the standard adjustments
for age of dam, sex of calf and 205 days, weaning weights of calves were affected by the experimental
treatments as follows:
1. Increased 88 lb. by creep feeding on fescue.
2. Increased 51 lb. by creep feeding on fescue-clover.
3. Increased 39 lb. by creep feeding on bluegrass.
4. Increased 38 lb. by creep feeding on bluegrass-clover.
5. Increased 33 lb. when grazing bluegrass compared with fescue.
6. Increased 23 lb. when grazing bluegrass-clover compared with fescue-clover.
7. Increased 36 lb. when grazing fescue-clover compared with fescue.
8. Increased 26 lb. when grazing bluegrass-clover compared with bluegrass.
Table 3. Three-year Average Performance of Calves
· Fescue Fescue Fescue Fescue Bluegrass Bluegrass Bluegrass Bluegrass
Nitrogen Nitrogen Clover Clover Nitrogen Nitrogen Clover Clover
No Creep Creep No Creep Creep N0 Creep Creep No Creep Creep
No. Calves 45 45 45 44 45 45 45 44
Birthweight, lb. 68 70 68 67 67 68 67 69
i Age at Weaning, days 226 219 224 223 221 225 221 223
· Actual Weaning wt., lb. 487 563 521 574 507 560 526 579
Adjusted Weaning wt.*, lb 472 560 508 559 505 544 531 569
*Adjusted for age of Dam, Sex of Calf and 205 Days
Table 4 shows that calves grazing fescue pasture used their creep feed much more efficiently than
calves on fescue-clover, bluegrass or bluegrass—clover. If it is reasoned that creep feeding corrects a
nutritional deficiency, obviously there was more of a nutritional deficiency for calves grazing fescue
pastures. Calves on fescue pasture may not have consumed as much of the fescue or the fescue may
have been more deficient in digestable energy than the other pasture forages. Another consideration is
that dams of calves on fescue pasture may not have provided as much milk for their calves. lt seems
obvious that there was more of a nutritional deficiency for calves grazing fescue and that creep feed
corrected the deficiency resulting in much better utilization of creep feed compared with the other
three pasture treatments.
Cow weight changes during the period May 20 to October 30 for the four different pastures are
shown in table 5. Cows grazing fescue-clover gained 32 pounds more during this period than cows
grazing straight fescue and cows grazing bluegrass-clover gained 60 pounds more than cows grazing
straight bluegrass. Cow gains for cows grazing either bluegrass or fescue were similar, with only a 17
_ pound difference in favor of bluegrass. Cows grazing bluegrass-clover pasture gained 45 pounds more
than those grazing fescue-clover. Although cows on the bluegrass-clover treatment were carrying
considerably more flesh at the time the calves were weaned, all cows appeared healthy and apparently
body weight gain was adequate for all cows.

Table 4. Efficiency of Creep Feed*
Kentucky 31 Fescue Kentucky Bluegrass
Ladino Ladino
Nitrogen Clover Nitrogen Clover
Adj. weaning wt.
Creep, lb. 560 559 544 569
Adj. weaning wt.
No creep, lb. 472 508 505 531
Gain due to creep, lb. 88 51 39 38
Creep per calf daily, lb. 4.7 4.6 4.4 4.3
Creep per calf, lb. 761 745 713 695
Creep/lb. added
gain, lb. 8.6 14.6 18.3 18.3
*Calves received creep from May 20 to October 30.
Table 5. Cow Weight Changes - Preweaning
Kentucky 31 Fescue Kentucky Bluegrass
Ladino Ladino j
Nitrogen Clover Nitrogen Clover
No. Cows 90 90 90 90
Initial Wt., lb.* 1066 1036 1042 1073
Average Wt., lb. 1083 1069 1068 1128
Final Wt.,lb.** 1100 1102 1093 1184
Cow Gain, lb. 34 66 51 111
*lnitial weight - May 20
**Final weight- October 30
No reproductive problems were experienced for cows on any of the different pasture treatments.
It has been reported that conception rate is often considerably lower for cows grazing straight fescue.
Possible reasons why no reproductive problems occurred in this study is feeding 3.5 pounds of corn
for a two-month period beginning two weeks before calving, pasture management with respect to
rotational grazing and clipping and the fact that about 20% of the available herbage in the fescue
pastures was other grasses which was largely bluegrass. .
The effect of creep feeding calves on cow weight changes during the last 163 days before weaning
is not clear. Table 6 shows that cows grazing either fescue or bluegrass, with creep fed calves gained
more than cows grazing the same pastures with calves which were not creep fed. However, cows

grazing either fescue-clover or bluegrass-clover with creep-fed calves gained less than cows grazing the
same type of pasture with non-creep fed calves.
L Table 6. Effect of Creep Feeding Calves on Cow Weight Changes
Kentucky 31 Fescue Kentucky Bluegrass
I Ladino Ladino
Nitrogen Clover Nitrogen Clover
· Calves Creep Fed
· No. Cows 45 45 45 45
Initial wt., lb.* 1 103 1019 1091 1046
Avg. wt.,lb. 1126 1044 1119 1094
Final wt., lb.** 1149 1070 1147 1139
. Cow Gain, lb. 46 52 56 93
Calves No Creep Feed
No. Cows 45 45 45 45
. Initial wt., 1b.* 1028 1054 992 1 101
Avg. wt., lb. 1040 1094 1015 1165
Final wt.,lb.** 1051 1133 1038 1230
Cow Gain, lb. 23 79 46 129
l *Initial weight - May 20
**Final weight - October 30
The amounts of feed fed during the winter to cows on each of the four different kinds of
pastures are given in table 7. It can be generalized that cows grazing fescue or fescue-clover pastures
were fed hay for about one-half as many days and were fed less than one-half as much total hay as
cows grazing bluegrass or bluegrass-clover pastures. Since the total amount of feed fed is considerably
below the National Research Council’s allowances for dry pregnant cows, pasture made a significant
contribution to cows on all four pasture treatments.
Table 7. Winter Feeding of Cows
Fescue Hay Bluegrass Hay Ground
_ Fescue Fescue Bluegrass Bluegrass Corn*
Nitrogen Clover Nitrogen Clover All Cows
No. days fed 54 64 107 110 69
Rate, lb./cow/day 6.8 5.9 6.8 7.7 3.5
Total/cow, lb. 367 378 728 847 242
*C0rn was fed from February 15 to April 25

Table 8 gives the amount of surplus pasture harvested as hay. Fescue and feseue-clover was more
productive than bluegrass and bluegrass—clover by about 26 tons. The grass—nitrogen treatment also
resulted in about 35 tons more pasture harvested as hay than the grass-clover treatment. It is realized
that hay yields are low and it should be pointed out that the demand for grazing had preference over ·
an attempt to get maximum hay yields. At times some fields were grazed for a while and then the _
surplus forage was harvested in the form of hay. It is also realized that legumes such as red clover or
alfalfa would improve yield of hay. In this study, surplus forage was harvested as hay to better .
measure total pasture productivity.
Table 8. Hay Production
Fescue Nitrogen Fescue Clover Bluegrass Nitrogen Bluegrass Clover
A cres A cres A cres A cres
Year Cut Tons Cut Tons Cut Tons Cut Tons
1974 45.5 26.0 ------ - ----- 38.0 10.6 13.4 2.5
1975 45.5 92.5 45.5 55.0 45.5 74.0 45.5 48.5
1976 38.0 24.5 ------ · ----- 13.4 11.6 ------ - -----
Avg. 43.0 47.7 15.2 27.5 32.3 32.1 19.6 17.0 .
The practice of creep feeding has been a controversial subject for some time. In the final analysis
whether to creep feed may be determined by the goal of the cow-calf producer. The higher price of _ '
feed grain in recent years makes creep feeding less attractive to the commercial producer. Also, if a
producer keeps his calves after weaning, he may be more concerned with total efficiency of produc-
tion with respect to the cow, calf and the pasture rather than maximum weaning weight. On the other
hand, the goal of a purebred producer may be to fully measure the genetic makeup of calves through
performance testing. In this case, creep feeding the calves may be advisable rather than providing
extremely high quality pasture which will fatten the cow excessively.
Whether to make a grass pasture more productive by applying nitrogen fertilizer or by intro-
ducing legumes into the grass stand is a management option to be contended with by Kentucky
cattlemen. Commercial nitrogen will increase productivity and the resulting pasture may be somewhat
easier to manage. Pasture productivity can also be increased by adding legumes and the legumes also
improve the quality of the pasture so that faster rate of gain of cattle result. In this case, cost of
production, quantity and quality of pasture as well as pasture management must be considered.
With respect to kind of grass, results of this experiment showed feseue to be more productive,
but bluegrass to be of higher quality relative to rate of gain of cows and calves. In the final analysis the
goals of each producer will determine the specific details of his pasture and herd management f

 ` 11
N. Gay, N. W. Bradley and]. A. Boling
Monensin sodium (Rumensin®) is a biologically active compound produced by the microorga-
‘ nism Streptomyces cinmzmonensis. Rumensin has been found to improve the utilization of feed at
various energy levels including all forage or hay rations. Generally, the feeding of Rumensin has
resulted in reduced feed intake. However this effect has depended on the level of Rumensin fed and
the energy concentration of the ration. This reduced feed requirement and feed intake has been
attributed to the influence of Rumensin on fermentation patterns in the rumen.
Acetic and propionic acids are produced in the rumen as end products of carbohydrate digestion.
On rations high in roughage, acetic acid predominates while high energy or grain rations result in
relatively less acetic and more proprionic acid being produced. Rumensin causes a shift toward
proprionic acid which is produced and utilized more efficiently from the standpoint of energy conver-
sion. After a certain level of proprionic acid is reached, cattle have a reduced appetite. Therefore the
. most efficient levels of Rumensin for different ration combinations is an important aspect of cattle
feeding which needs to be determined.
Rumensin is presently approved for use in feedlot rations. It will likely be approved for use with
grazing cattle when sufficient data is available. A withdrawal period is not necessary since no residues
. have been found following slaughter of Rumensin fed cattle. Various studies with Rumensin have been
_ conducted by UK researchers, some of which are reported here. Results show in general that
Rumensin saves 10-15% in feed required per unit of gain. Its influence on rate of gain is not as
consistent as its influence on improved feed utilization, but growth gains can be expected to be
improved and finishing gains not influenced to a very great extent.
J. A. Boling, N. W. Bradley and L. D. Campbell
Seventy-two Angus steer calves were utilized in a grazing trial to determine the influence of level
. of monensin on rate of gain. They were randomly allotted to 4 treatment groups of 18 steers each.
The 4 treatment groups were: (1) control, (2) 25 mg, (3) 50 mg and (4) 100 mg monensin per head
daily. The monensin was mixed with ground shelled corn and fed at a level of 0.91 kg per steer daily.
The 4 groups of steers were randomly assigned initially to four 4.86 hectare pastures containing a
Kentucky bluegrass—clover mixture. The steers were rotated weekly among the 4 experimental pastures
. for the duration of the grazing period.
The initial weights and average daily gains are presented in table 1. Steers which were fed 25 mg
monensin per day had the same gains as the control steers. Steers fed 50 mg or 100 mg monensin per
head daily had higher average daily gains than those fed either no monensin or 25 mg monensin per
head daily. These data indicate that improved gains in growing cattle can be expected by feeding 50 or
100 mg monensin per head daily during the summer grazing period.

Table 1. Body Weights and Average Daily Gain of Steers Fed Different
Levels of Monensin Throughout the Grazing Perioda
Level of Monensinlday
Control 25mg 50mg 100mg ·
No. steersb 18 17 18 18
Initial wt., kg 209.4 212.6 209.8 211.5
Final wt., kg 287.3 289.0 311.7 307.2
ADG, kg .55° .55° .75d .58d
aLength of the trial was 140 days (May 4 to October 23)
bOne steer died in the 25 mg treatment group.
°dMeans on the same line bearing different superscripts differ
significantly (P ( .01).
_]. A. Boling, N. W. Bradley and L. D. Campbell
Ninety-six Hereford and Charolais-crossbred steers were utilized in a study to determine the
influence of level of monensin on growth and feed efficiency of finishing steers. The steers were
randomly allotted to 12 groups of eight steers each. The 12 groups were randomly assigned to 4
treatments of 3 pens per treatment. The 4 treatment groups were fed the grain supplement presented
in table 1 in which monensin replaced corn to provide the following levels of monensin per 4.54 kg of
grain supplement: (1) control, (2) 100 mg, (3) 200 mg or (4) 300 mg monensin per steer daily. In
addition, they were offered corn silage ad libiturn.
Table 1. Composition of Grain Supplement Fed to
Finishing Steers
Ingredient Percent
Ground shelled corn 86.3
Soybean meal (44% C.P.) 8.6
Urea (45% N) 1.6
Dicalcium phosphate 2.5
Salt 1.0
Vitamin Aa +
3‘Vitamin A was added at a level to provide 20,000
IU per 4.54 kg grain supplement.

 ‘ 13
V Growth and feed efficiency of steers fed different levels of monensin for the 157-day trial are
presented in table 2. Steers fed all levels of monensin had small nonsignificant increases in average
daily gain. Feed intake decreased slightly as level of monensin fed increased. Feed efficiency was
improved by all levels of monensin fed. Also, a small improvement in feed efficiency was observed as
_ the level of monensin fed was increased from 100 mg to 300 mg monensin per head daily. The
improved feed efficiency is consistent with that observed in many other studies with finishing cattle.
Table 2. Growth, Feed Intake and Efficiency of Steers Fed Different
Levels of Monensina
Level of monenslnldaiy
( Control 1 0Omg 200mg 300mg
No. steers 24 24 24 24
_ Initial wt., shrunk (kg) 302.0 300.2 303.7 300.4
ADG, kg 1.14 1.26 1.23 1.18
Corn silage/ day
(dry matter), kg 4.13 3.64 3.31 3.00
Grain suppl/ day
(dry matter), kg 4.05 4.03 3.99 3.90
Feed/ gain (dry matter
basis) 7.26b 6.08C 5.92c 5.88C
Carcass data collected at the termination of the trial are presented in table 3. Carcass weight,
U.S.D.A. grade, yield grade and dressing percentage did not differ significantly among the four treat-
· ment groups of steers.
Table 3. Carcass Characteristics of Steers Fed Different Levels of
Monensin (157 Days)
Level 0fMonensz`nlday
Control 100mg 200 mg 300mg
Carcass wt., kg 298.8 308.3 304.6 293.6
U.S.D.A. gradea 9.5 9.5 9.0 8.5
Yield grade 2.2 2.5 2.5 2.3
V Dressing% 62.3 61.4 61.3 60.5
aU.S.D.A. grade. 9 = good —, 10 = good, 11 = good +.

W. W. Steen, N. Gay,]. A. Boling, N. W. Bradley,
_]. W. McCormick and L. C. Pendlum
Decreased feed intake, improved feed efficiency and gain responses as a result of feeding
Rumensin has been reported by various researchers. Results are uniform, with respect to improvement
in feed efficiency; however, gain response is variable depending on ration composition and level of
Rumensin. In general the effects of Rumensin on carcass traits have been minimal.
The purpose of this study was to: (1) observe the response of feedlot steers to Rumensin level;
(2) observe the effect of altering the level of Rumensin based on feed intake; (3) determine the effect
of Rumensin on carcass traits and liver abcesses.
Ninety-six crossbred yearling steers were randomly allotted to four treatments on the basis of =
weight and breeding. The levels of Rumensin were as follows: A-control; B-100 mg; C-200 mg; and
D-variable levels depending on feed consumption as follows: initially, 150 mg until day 28 of the trial;
then 200 mg until day 56; followed by 250 mg until day 84 and finally 300 mg Rumensin per head
daily until termination at day 183.
The control ration consisted of corn silage fed to appetite, ground shelled corn, initially fed at
four pounds per head daily and increased to an average final level of 8.4 pounds (dry matter basis) per
head daily, and soybean meal (44%) fed at 1.33 pounds, Salt, trace mineralized salt and steamed bone
meal were fed free choice. The Rumensin treatments were the same as the control except for the
additions previously described. Initial full and shrunk weights were obtained, as well as full weights
every 28 days throughout the experiment. These were used in adjusting feed intake and Rumensin
At the start of the study, all cattle were implanted with 36 mg DES, wormed, vaccinated for IBR,
P13, leptospirosis and injected with vitamins A, D and E. Following 183 days on feed, cattle were
slaughtered at a cooperating packing plant and carcass data obtained following a 48 hour chill.
Feed intake, feed efficiency and daily gains are shown in table 1. Steers fed either 200 mg or the
variable level of Rumensin consumed less corn silage and less total ration than the control or 100 mg
groups. Feed efficiency was improved by all levels of Rumensin, the 200 mg level giving the greatest
improvement. The average feed saving due to Rumensin was 12%. All Rumensin fed groups had
significantly greater average daily gains than the control group.
Carcass data are presented in table 2 and showed no difference in dressing percent or incidence of
liver condemnations. Rumensin fed steers had significantly heavier carcasses, more internal and
external fat. Quality grade was not influenced, however, yield grades were different due to fatter

 I 15
Table 1. Effect of Rumcnsin Levels on Dry Matter Intake, Daily Gains and Feed
` Efficiency
I Treatment (mg Rumensinghdlday 
Item 0 100 200 Variable
No. steers 30 30 30 30
Avg. start. wt., lb. 528 524 521 517
Avg. end. wt., lb. 942 970 986 968
ADG, lb. 2.27 2.46 2.53 2.46
Avg daily ration, lb.
Corn silage 10.1 9.8 9.2 9.1
Ground corn 6.6 6.7 6.7 6.6
Soybean meal 1.3 1.3 1.3 1.3
Total dry matter 18.1 17.8 17.3 17.1
F/G 8.0 7.2 6.8 7.0
% of Control -------- 92 85 88
Table 2. Effects of Rumcnsin Levels on Carcass Characteristics
Treatment (mg Rumenszhlltdrday 
Item 0 100 200 Variable
Dressing% 63.4 63.3 63.6 63.2
Hot carcass wt., lb. 596 614 627 612
U.S.D.A. quality grade} 7.3 7.5 7.2 7.9
U.S.D.A. yield grade 2.8 3.1 3.1 3.2
Liver abcesses % 20 10 20 33
lquality grades, good + = 6, Choice - = 7, Choice O = 8
A N. Gay,]. A. Boling, N. W. Bradley, D. Lovell,]. R. Overfield
and W. R. Selman
Since the relative price of feed grains and fed beef vary over time, the response of finishing cattle
to different kinds and levels of grain with and without Rumcnsin needs to be clarified. Previously
reported studies of this type have not used wheat as a ration ingredient. The objective of this study

was to determine the response of feedlot cattle to different levels of corn and wheat, with and without
Monensin. I
A total of 192 yearling steers were used in two experiments at two locations. Corn was fed at two
levels at one location and wheat at two levels at another location. Rumensin was fed at 0 and 300 mg ’
per head per day across grain levels, after the initial 28 days, during which time 100 mg was fed.
Cattle were crossbred, yearlings in medium flesh, which had been accustomed to their respective
rations prior to the start of the study. Within each experiment, 96 cattle were allotted to 12 pens of 8
each on the basis of weight and breed. Each animal was implanted with 30 mg of DES, wormed,
vaccinated for IBR, P13 , leptospirosis, blackleg and malignant edema, and injected with vitamins A, D
and E.
Cattle were weighed initially, full and following a 24-hour fast, and at 28 day intervals thereafter.
Ration adjustments were made on the basis of 28-day weights and feed consumption was calculated at
corresponding times. Following final full and shrunk weights, cattle were transported to a packing
plant for slaughter and collection of carcass data.
Rations consisted of corn or wheat, whole plant corn silage and soybean meal, Salt, trace-
mineralized salt and steamed bone meal were offered free choice in a 3 compartment feeder. Grain
levels were adjusted to 1% or (a full feed) 1.6% of liveweight. Soybean meal was fed at 1.0 and 1.5
pounds daily with the wheat and com rations, respectively. All rations were fed once daily and
adjusted to allow ad libitum intake. Wheat was coarse cracked and corn ground. Rumensin was added
at 0 or 300 mg to the soybean meal, after the first 28 day period and at O or 100 mg during that time.
Rumen samples were takenjust prior to termination of the 140 day studies via stomach tube and A
analyzed for total and molar percent, of individual volatile fatty acids.
Careass data were collected following a 48 hour chill. Percent kidney, pelvic and heart fat was
visually estimated. Quality grades were determined by a U.S.D.A. grader and yield grades were calcu-
lated from fat thickness, ribeye area, carcass weight and percent kidney, pelvic and heart fat.
Performance and feed data for corn fed cattle are presented in table 1. Gains and final shrunk
weights were influenced by only one treatment, low grain control. Rumensin with low grain resulted
in gains equal to high grain. Both grain levels and Rumensin levels resulted in significantly different
daily dry matter intakes. Low grain treatments ate more TDN on the average. The high-grain
Rumensin fed cattle ate less than non-Rumensin fed cattle. Feed efficiency was improved more on the
low grain treatment by Rumensin, 17 vs. 3%.
Wheat fed cattle performance and feed data is seen in table 2. Again, final shrunk weights were
significantly lower for the low grain control treatment. Rumensin fed with the low grain level resulted
in gains similar to high grain without Rumensin. In this trial, grain level did not influence dry matter
intake. Rumensin fed cattle consumed significantly less dry matter than non-Rumensin fed. This
resulted in 8.5 and 14.2% improvement in feed utilization due to Rumensin in low and high grain
treatments, respectively.
Carcass data for corn fed cattle are presented in table 3. No differences were noted except a
lower hot carcass weight for low-grain control cattle.
Carcass data for wheat fed cattle, seen in table 4, also revealed no differences except for hot
carcass weight. Higher grain level treatments tended to be fatter.
Observations on ruminal VFA production are seen in tables 5 and 6. A significant reduction in
acetic and a concurrent increase in proprionic acids were seen for both grain and Rumensin additions.